This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The purpose of this research is to develop a quantitative structural analysis relationship (QSAR) between the toxicity of pharmaceutical compounds and personal care products (PPCPs) and their chemical composition. In the first year of research using the super computer, an organizing principle with which to predict and understand the biotransformation of (PPCPs) was developed. Frontier electron density (FED), coupled with previous laboratory research and literature on the degradation of PPCPs, was used to develop a model for predicting the biotransformation pathways. The focus of this years research is to determine the change in toxicity as a function of biotransformation. The hypothesis is that the toxicity will be related to the hydrophobicity of the parent compounds and their metabolites and that the toxicity will depend on which ring is cleaved first in the metabolic pathway. We are testing this hypothesis for various PPCPs, including Estriol, 17? Ethinylestradiol, Estrone, and 17 ? Estradiol.